The present invention generally relates to power detection systems and more particularly to parallel harness current imbalance and failure detection.
High-power electronics play a significant role in the modern aircraft and automotive industry. This is particularly true in the area of traction drive applications for aircraft and ground vehicles. The commercial aircraft business is moving toward more fuel efficient and environmental friendly traction drive operations. One example from this latest trend is the electrical taxi application for the Airbus A320 NEO airplane. In the Airbus A320 NEO, the airplane will be using an auxiliary power unit (APU) to power the electric drive system to taxi into and/or out from a runway. All or part of the airplane's engines will be turned off during taxiing to save fuel. The electric drive system contains an autotransformer rectifier unit (ATRU), a motor controller/inverter, a gearbox, and a traction motor. The benefits of an electrical taxi system include reduction of fuel consumption, brake wear, and ground tug operation.
Military ground vehicles have migrated toward hybrid electric technology where some vehicles employ main propulsion from electric drives. Substantial demand for power utilization increases when using more electric technology to propel the vehicle. Thus, a significant increased usage in high-power harnesses for the electric drive system results from the demand for more power. In some applications, a set of 3-phase high-power harnesses may be used to bring 3-phase 115-VAC at 400 Hz from the APU to the ATRU to generate a high-voltage DC source for the motor controller/inverter. A power distribution harness may be used to deliver a high-voltage DC source from the ATRU to the motor controller/Inverter. A set of 3-phase cables may connect the motor controller/inverter outputs to drive the traction motor with AC voltage/current generated from the motor controller. The harness may carry the high load current that is necessary to deliver high torque (such as breakaway torque) and acceleration for vehicles/airplanes to reach a desired taxi speed.
In conventional power systems for taxi systems, for example hydraulic brakes, 1 kilowatt was adequate to power the system. Thus smaller radius wires are sufficient for routing in the system. However, for the increased power requirements of the power aforementioned distribution harnesses, routing constraints of the vehicle as well as the current carrying capacity may require thicker wiring. For example, some electric applications may use 50-kW-60 kW to the taxi system fed from the fuselage. Due to additional environmental and space constraints (such as routing and bending of cables for retrofitting an existing system), there may be a need to parallel the harness with smaller wires to meet the power and current rating of the system. The parallelization creates new challenges. The paralleled wires may be difficult to impedance match and result in imbalanced currents to circulate in the taxi system that may create power losses and heat.
As can be seen, there is a need for detection that monitors for imbalanced current in 3-phase power systems in vehicles.